G'day Darey

I agree with your asking the question - it is correct to do so
To take it into another direction - but not steal the thread- as I see it, it comes down to the result as seen, printed and displayed on the wall.

Looking at an image on a computer screen, a 1megapixel screen at that, will never show us the lens's true capabilities & performance
It seems to me [and I am guilty too] that far too many of us only view our images on-screen and as such, sharpness is a visual illusion ... it is not until we view the image as a 16x24" or 20x30" poster that we can truly see the qualities of a good lens

Then also, you get the vagaries of flare from back lighting/cross lighting, colour fringing at the long end, etc etc
Regards, Phil